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Papers by Terry Tritt

Research paper thumbnail of Relaxation of charge-density-wave metastable states atT<4.2 K inNbSe3as evidenced in the Shubnikov–de Haas oscillations

Physical Review B

%e present a study of charge-density-wave metastable states below 4.2 K in thermally quenched NbS... more %e present a study of charge-density-wave metastable states below 4.2 K in thermally quenched NbSe3. These states and their ensuing relaxation are manifest most strongly in the Shubnikov-de Haas (SdH) oscillations. The quenched metastable state remains without any change for time scales ranging from several minutes to several hours before a sharp relaxation is observed. Sharp jumps in the magnetoresistance and the amplitudes of the SdH oscillations are observed when the metastable states relax spontaneously. %'e present evidence that these relaxations are not driven by the magnetic field, H, the current, or a combination of the two. The SdH oscillation frequencies with H parallel to c indicate a 12% decrease in the extremal area of the conduction-electron Fermi surface after relaxation to the equilibrium state. However, the determination of the Hall coefhcient suggests that this change is not simply related to a change in the carrier concentration.

Research paper thumbnail of Change in Young’s modulus at low frequency upon charge-density-wave depinning inTaS3

Physical Review B, 1991

ABSTRACT

Research paper thumbnail of Effect of Rare-Earth Doping on the Electrical Resistivity and Thermopower of the Transition Metal Pentatelluride HfTe_5

The transition metal pentatellurides HfTe5 and ZrTe5 exhibit semimetallic resistivity except for ... more The transition metal pentatellurides HfTe5 and ZrTe5 exhibit semimetallic resistivity except for a large resistive peak as a function of temperature at around 75 K for HfTe5 and 145 K for ZrTe_5. At a temperature corresponding to this peak, the thermopower crosses zero as it moves from large positive values to large negative values. Previous doping studies have shown profound

Research paper thumbnail of Transport and magnetism in La��Ca��(Mn{sub 1-x}Co�)O� and La��Ca��(Mn{sub 1-x}Ni�)O� (abstract)

Research paper thumbnail of High-Temperature Thermoelectric Properties of Co 4 Sb 12 -Based Skutterudites with Multiple Filler Atoms: Ce 0.1 In x Yb y Co 4 Sb 12

Research paper thumbnail of Selection Criteria for New Materials For Thermoelectric Applications

Research paper thumbnail of Thermoelectric Properties of Stable Icosahedral Phase Quasicrystals

Research paper thumbnail of Thermoelectric Properties of the Crystalline Cd_6Yb Material

Research paper thumbnail of High temperature electrical transport in Al-Pd-Mn quasicrystals

Eighteenth International Conference on Thermoelectrics. Proceedings, ICT'99 (Cat. No.99TH8407), 1999

We report measurements of the electrical conductivity σ(T) and the Seebeck coefficient α(T) of a ... more We report measurements of the electrical conductivity σ(T) and the Seebeck coefficient α(T) of a Czochralski-grown single phase quasicrystal of icosahedral Al 70.8 Pd 20.9 Mn 8.3 in the temperature range between 5 and 600 K. The electrical conductivity σ(T) is only weakly temperature dependent. The values of the conductivity fall in the range between 630 and 740 (Ω cm)-1. The Seebeck coefficient, α(T), increases monotonically with increasing temperature, reaches a maximum of 110 µV/K at around 500 K after which the thermopower begins to decrease with increasing temperature. The power factor, α 2 σT, is obtained from the electrical conductivity and thermopower data and at T = 600 K, the power factor of icosahedral Al 70.8 Pd 20.9 Mn 8.3 reaches 0.5 W/m-K. This indicates that quasiperiodically structured alloys may be promising materials for thermoelectric applications at temperatures above room temperature.

Research paper thumbnail of Effects of the addition of Co on the thermoelectric properties of the AlPdMn quasicrystalline system

Eighteenth International Conference on Thermoelectrics. Proceedings, ICT'99 (Cat. No.99TH8407), 1999

Research paper thumbnail of Solution Chemical Synthesis of nanostructured Thermoelectric Materials

Research paper thumbnail of Specific Heat and Hall Effect of the Rare Earth Diantimonides

We have measured the temperature dependence between 4.2 K and 300 K of the specific heat (Cp) and... more We have measured the temperature dependence between 4.2 K and 300 K of the specific heat (Cp) and Hall effect (RH)* of the layered RESb2 compounds PrSb2, LaSb2, NdSb2, CeSb2, and SmSb2. Cp measurements were performed using ac technique as well as adiabatic technique. Low temperature cusps were observed in PrSb2, NdSb2, CeSb2 and SmSb2 in both adiabatic and ac Cp. These cusps are associated with the magnetic transitions, reported earlier. For LaSb2, Cp can be fitted using an electronic and lattice component. The large peaks in Cp of PrSb2, NdSb2, and CeSb2 are suppressed by magnetic field directed along the c-axis. No magnetic field effect is observed in this orientation for the anomaly in SmSb2. High resolution ac calorimetry did not reveal any cusp associated with the 38 K resistance anomaly observed in NdSb2. This may suggest that the 38 K anomaly in NdSb2 may have a different origin than the 98 K anomaly in PrSb2. Additional Hall effect measurements will be presented and discusse...

Research paper thumbnail of A novel approach to thermoelectrics materials research of skutterudites

Seventeenth International Conference on Thermoelectrics. Proceedings ICT98 (Cat. No.98TH8365), 1998

In recent years, attention has been refocused on thermoelectric materials research because of the... more In recent years, attention has been refocused on thermoelectric materials research because of the interesting crystal structure and transport properties of the skutterudite family of compounds. The interest in this material system arises from its marked reduction in lattice thermal conductivity where the voids in the crystal structure are filled with “guest” atoms. The disorder resulting from these atomic inclusions

Research paper thumbnail of Chapter 2 Overview of measurement and characterization techniques for thermoelectric materials

Semiconductors and Semimetals, 2001

ABSTRACT

Research paper thumbnail of Thermoelectric behaviour of p- and n- type Ti-Ni-Sn half Heusler alloy variants and their amorphous equivalents

MRS Proceedings, 2013

ABSTRACTTi-Ni-Sn type half-Heusler alloys which have the versatility to be either p- or n-type de... more ABSTRACTTi-Ni-Sn type half-Heusler alloys which have the versatility to be either p- or n-type depending on the type of substitution, have been synthesized and investigated in the present work. The added advantage of doping them with multiple elements is that they will be amenable to bulk amorphous phase formation. The hole doped alloys were predominantly single phase with a cubic structure, while the electron doped alloys were found to have minor additional phases. All the alloys exhibit extremely weak metallic-like or degenerate semiconductor transport behaviour in the temperature range 20 K to 1000 K. The resistivity of p-type alloys exhibits semi-metallic-to-semiconducting transition at ∼ 500 K while the n-type alloys exhibit a weak metallic-like behaviour in the complete temperature range. The Seebeck coefficient has strong temperature dependence with a maximum of 45 μV K−1 in the temperature range 600-700 K in the p-type alloys. The n-type alloys however exhibit a linear varia...

Research paper thumbnail of New insights on the synthesis and electronic transport in bulk polycrystalline Pr-doped SrTiO3−δ

Journal of Applied Physics, 2015

Research paper thumbnail of Significant enhancement in thermoelectric properties of polycrystalline Pr-doped SrTiO3−δ ceramics originating from nonuniform distribution of Pr dopants

Applied Physics Letters, 2014

Recently, we have reported a significant enhancement (>70% at 500 C) in the thermoelectric power ... more Recently, we have reported a significant enhancement (>70% at 500 C) in the thermoelectric power factor (PF) of bulk polycrystalline Pr-doped SrTiO 3 ceramics employing a novel synthesis strategy which led to the highest ever reported values of PF among doped polycrystalline SrTiO 3. It was found that the formation of Pr-rich grain boundary regions gives rise to an enhancement in carrier mobility. In this Letter, we investigate the electronic and thermal transport in Sr 1Àx Pr x TiO 3 ceramics in order to determine the optimum doping concentration and to evaluate the overall thermoelectric performance. Simultaneous enhancement in the thermoelectric power factor and reduction in thermal conductivity in these samples resulted in more than 30% improvement in the dimensionless thermoelectric figure of merit (ZT) for the whole temperature range over all previously reported maximum values. Maximum ZT value of 0.35 was obtained at 500 C. V

Research paper thumbnail of Nanostructured bulk thermoelectric materials and their properties

ICT 2005. 24th International Conference on Thermoelectrics, 2005., 2005

Advanced bulk thermoelectric materials have been developed by fabricating composites of uniformly... more Advanced bulk thermoelectric materials have been developed by fabricating composites of uniformly distributed thermoelectric nanoparticles within a high surface area semiconductor matrix. In this composite structure, constituents of the thermoelectric materials' figure of merit can be decoupled and controlled independently, and consequently, one can achieve a high thermoelectric figure of merit. The produced composites exhibited extremely low thermal conductivity and relatively high electrical conductivity. However, the Seebeck coefficient was relatively low, probably due to poor quality of the thermoelectric particles. In an in-plane test geometry (van der Pauw configuration), the electrical resistivity of the composite sample decreased continuously as temperature increased, a typical semiconductor behavior. In the perpendicular-to-the-plane (cross-plane) test geometry, electrical resistance of the sample increased continuously with increasing temperature, probably a semi-metallic behavior. This anisotropy in the electrical resistance was reproducible. We also observed relatively strong high frequency AC-signals in the in-plane test geometry samples.

Research paper thumbnail of Modeling Thermopower in AlPdMn Based Quasicrystalline Systems

MRS Proceedings, 2000

We report room temperature thermopower values and the temperature dependence for several AlPdMn b... more We report room temperature thermopower values and the temperature dependence for several AlPdMn based quasicrystals. In an effort to further understand the complexities of electrical transport in quasicrystalline systems, thermopower data for icosahedral Al71Pd21Mn8-XReX will be presented and discussed. A relation of room temperature thermopower to the curvature of the thermopower is demonstrated. We propose an empirical fit to the thermopower data, utilizing three free variables. The physical significance of the fit parameters is discussed. These results are discussed in brief concerning the relation to the application of quasicrystals for use as thermoelectric materials.

Research paper thumbnail of Large enhancement of the resistive anomaly in the pentatelluride materials HfTe5 and ZrTe5 with applied magnetic field

Physical Review B, 1999

The resistivity of single-crystal pentatellurides, HfTe 5 and ZrTe 5 , has been measured as a fun... more The resistivity of single-crystal pentatellurides, HfTe 5 and ZrTe 5 , has been measured as a function of temperature and applied magnetic field. At zero magnetic field these materials exhibit a peak in their resistivity ͑at T P) as a function of temperature that corresponds to an, as yet, undetermined phase transition. The application of a transverse magnetic field ͑B Ќ to the current I͒ has a profound effect on the resistive peak in these materials, shifting the peak to slightly higher temperatures and producing a large enhancement of the resistivity at the peak, up to a factor of 3 in ZrTe 5 (T P ϭ145 K͒ and 10 in HfTe 5 (T P ϭ80 K͒. Larger magnetoresistance is observed at even lower temperatures, TϽ20 K. ͓S0163-1829͑99͒06035-X͔

Research paper thumbnail of Relaxation of charge-density-wave metastable states atT<4.2 K inNbSe3as evidenced in the Shubnikov–de Haas oscillations

Physical Review B

%e present a study of charge-density-wave metastable states below 4.2 K in thermally quenched NbS... more %e present a study of charge-density-wave metastable states below 4.2 K in thermally quenched NbSe3. These states and their ensuing relaxation are manifest most strongly in the Shubnikov-de Haas (SdH) oscillations. The quenched metastable state remains without any change for time scales ranging from several minutes to several hours before a sharp relaxation is observed. Sharp jumps in the magnetoresistance and the amplitudes of the SdH oscillations are observed when the metastable states relax spontaneously. %'e present evidence that these relaxations are not driven by the magnetic field, H, the current, or a combination of the two. The SdH oscillation frequencies with H parallel to c indicate a 12% decrease in the extremal area of the conduction-electron Fermi surface after relaxation to the equilibrium state. However, the determination of the Hall coefhcient suggests that this change is not simply related to a change in the carrier concentration.

Research paper thumbnail of Change in Young’s modulus at low frequency upon charge-density-wave depinning inTaS3

Physical Review B, 1991

ABSTRACT

Research paper thumbnail of Effect of Rare-Earth Doping on the Electrical Resistivity and Thermopower of the Transition Metal Pentatelluride HfTe_5

The transition metal pentatellurides HfTe5 and ZrTe5 exhibit semimetallic resistivity except for ... more The transition metal pentatellurides HfTe5 and ZrTe5 exhibit semimetallic resistivity except for a large resistive peak as a function of temperature at around 75 K for HfTe5 and 145 K for ZrTe_5. At a temperature corresponding to this peak, the thermopower crosses zero as it moves from large positive values to large negative values. Previous doping studies have shown profound

Research paper thumbnail of Transport and magnetism in La��Ca��(Mn{sub 1-x}Co�)O� and La��Ca��(Mn{sub 1-x}Ni�)O� (abstract)

Research paper thumbnail of High-Temperature Thermoelectric Properties of Co 4 Sb 12 -Based Skutterudites with Multiple Filler Atoms: Ce 0.1 In x Yb y Co 4 Sb 12

Research paper thumbnail of Selection Criteria for New Materials For Thermoelectric Applications

Research paper thumbnail of Thermoelectric Properties of Stable Icosahedral Phase Quasicrystals

Research paper thumbnail of Thermoelectric Properties of the Crystalline Cd_6Yb Material

Research paper thumbnail of High temperature electrical transport in Al-Pd-Mn quasicrystals

Eighteenth International Conference on Thermoelectrics. Proceedings, ICT'99 (Cat. No.99TH8407), 1999

We report measurements of the electrical conductivity σ(T) and the Seebeck coefficient α(T) of a ... more We report measurements of the electrical conductivity σ(T) and the Seebeck coefficient α(T) of a Czochralski-grown single phase quasicrystal of icosahedral Al 70.8 Pd 20.9 Mn 8.3 in the temperature range between 5 and 600 K. The electrical conductivity σ(T) is only weakly temperature dependent. The values of the conductivity fall in the range between 630 and 740 (Ω cm)-1. The Seebeck coefficient, α(T), increases monotonically with increasing temperature, reaches a maximum of 110 µV/K at around 500 K after which the thermopower begins to decrease with increasing temperature. The power factor, α 2 σT, is obtained from the electrical conductivity and thermopower data and at T = 600 K, the power factor of icosahedral Al 70.8 Pd 20.9 Mn 8.3 reaches 0.5 W/m-K. This indicates that quasiperiodically structured alloys may be promising materials for thermoelectric applications at temperatures above room temperature.

Research paper thumbnail of Effects of the addition of Co on the thermoelectric properties of the AlPdMn quasicrystalline system

Eighteenth International Conference on Thermoelectrics. Proceedings, ICT'99 (Cat. No.99TH8407), 1999

Research paper thumbnail of Solution Chemical Synthesis of nanostructured Thermoelectric Materials

Research paper thumbnail of Specific Heat and Hall Effect of the Rare Earth Diantimonides

We have measured the temperature dependence between 4.2 K and 300 K of the specific heat (Cp) and... more We have measured the temperature dependence between 4.2 K and 300 K of the specific heat (Cp) and Hall effect (RH)* of the layered RESb2 compounds PrSb2, LaSb2, NdSb2, CeSb2, and SmSb2. Cp measurements were performed using ac technique as well as adiabatic technique. Low temperature cusps were observed in PrSb2, NdSb2, CeSb2 and SmSb2 in both adiabatic and ac Cp. These cusps are associated with the magnetic transitions, reported earlier. For LaSb2, Cp can be fitted using an electronic and lattice component. The large peaks in Cp of PrSb2, NdSb2, and CeSb2 are suppressed by magnetic field directed along the c-axis. No magnetic field effect is observed in this orientation for the anomaly in SmSb2. High resolution ac calorimetry did not reveal any cusp associated with the 38 K resistance anomaly observed in NdSb2. This may suggest that the 38 K anomaly in NdSb2 may have a different origin than the 98 K anomaly in PrSb2. Additional Hall effect measurements will be presented and discusse...

Research paper thumbnail of A novel approach to thermoelectrics materials research of skutterudites

Seventeenth International Conference on Thermoelectrics. Proceedings ICT98 (Cat. No.98TH8365), 1998

In recent years, attention has been refocused on thermoelectric materials research because of the... more In recent years, attention has been refocused on thermoelectric materials research because of the interesting crystal structure and transport properties of the skutterudite family of compounds. The interest in this material system arises from its marked reduction in lattice thermal conductivity where the voids in the crystal structure are filled with “guest” atoms. The disorder resulting from these atomic inclusions

Research paper thumbnail of Chapter 2 Overview of measurement and characterization techniques for thermoelectric materials

Semiconductors and Semimetals, 2001

ABSTRACT

Research paper thumbnail of Thermoelectric behaviour of p- and n- type Ti-Ni-Sn half Heusler alloy variants and their amorphous equivalents

MRS Proceedings, 2013

ABSTRACTTi-Ni-Sn type half-Heusler alloys which have the versatility to be either p- or n-type de... more ABSTRACTTi-Ni-Sn type half-Heusler alloys which have the versatility to be either p- or n-type depending on the type of substitution, have been synthesized and investigated in the present work. The added advantage of doping them with multiple elements is that they will be amenable to bulk amorphous phase formation. The hole doped alloys were predominantly single phase with a cubic structure, while the electron doped alloys were found to have minor additional phases. All the alloys exhibit extremely weak metallic-like or degenerate semiconductor transport behaviour in the temperature range 20 K to 1000 K. The resistivity of p-type alloys exhibits semi-metallic-to-semiconducting transition at ∼ 500 K while the n-type alloys exhibit a weak metallic-like behaviour in the complete temperature range. The Seebeck coefficient has strong temperature dependence with a maximum of 45 μV K−1 in the temperature range 600-700 K in the p-type alloys. The n-type alloys however exhibit a linear varia...

Research paper thumbnail of New insights on the synthesis and electronic transport in bulk polycrystalline Pr-doped SrTiO3−δ

Journal of Applied Physics, 2015

Research paper thumbnail of Significant enhancement in thermoelectric properties of polycrystalline Pr-doped SrTiO3−δ ceramics originating from nonuniform distribution of Pr dopants

Applied Physics Letters, 2014

Recently, we have reported a significant enhancement (>70% at 500 C) in the thermoelectric power ... more Recently, we have reported a significant enhancement (>70% at 500 C) in the thermoelectric power factor (PF) of bulk polycrystalline Pr-doped SrTiO 3 ceramics employing a novel synthesis strategy which led to the highest ever reported values of PF among doped polycrystalline SrTiO 3. It was found that the formation of Pr-rich grain boundary regions gives rise to an enhancement in carrier mobility. In this Letter, we investigate the electronic and thermal transport in Sr 1Àx Pr x TiO 3 ceramics in order to determine the optimum doping concentration and to evaluate the overall thermoelectric performance. Simultaneous enhancement in the thermoelectric power factor and reduction in thermal conductivity in these samples resulted in more than 30% improvement in the dimensionless thermoelectric figure of merit (ZT) for the whole temperature range over all previously reported maximum values. Maximum ZT value of 0.35 was obtained at 500 C. V

Research paper thumbnail of Nanostructured bulk thermoelectric materials and their properties

ICT 2005. 24th International Conference on Thermoelectrics, 2005., 2005

Advanced bulk thermoelectric materials have been developed by fabricating composites of uniformly... more Advanced bulk thermoelectric materials have been developed by fabricating composites of uniformly distributed thermoelectric nanoparticles within a high surface area semiconductor matrix. In this composite structure, constituents of the thermoelectric materials' figure of merit can be decoupled and controlled independently, and consequently, one can achieve a high thermoelectric figure of merit. The produced composites exhibited extremely low thermal conductivity and relatively high electrical conductivity. However, the Seebeck coefficient was relatively low, probably due to poor quality of the thermoelectric particles. In an in-plane test geometry (van der Pauw configuration), the electrical resistivity of the composite sample decreased continuously as temperature increased, a typical semiconductor behavior. In the perpendicular-to-the-plane (cross-plane) test geometry, electrical resistance of the sample increased continuously with increasing temperature, probably a semi-metallic behavior. This anisotropy in the electrical resistance was reproducible. We also observed relatively strong high frequency AC-signals in the in-plane test geometry samples.

Research paper thumbnail of Modeling Thermopower in AlPdMn Based Quasicrystalline Systems

MRS Proceedings, 2000

We report room temperature thermopower values and the temperature dependence for several AlPdMn b... more We report room temperature thermopower values and the temperature dependence for several AlPdMn based quasicrystals. In an effort to further understand the complexities of electrical transport in quasicrystalline systems, thermopower data for icosahedral Al71Pd21Mn8-XReX will be presented and discussed. A relation of room temperature thermopower to the curvature of the thermopower is demonstrated. We propose an empirical fit to the thermopower data, utilizing three free variables. The physical significance of the fit parameters is discussed. These results are discussed in brief concerning the relation to the application of quasicrystals for use as thermoelectric materials.

Research paper thumbnail of Large enhancement of the resistive anomaly in the pentatelluride materials HfTe5 and ZrTe5 with applied magnetic field

Physical Review B, 1999

The resistivity of single-crystal pentatellurides, HfTe 5 and ZrTe 5 , has been measured as a fun... more The resistivity of single-crystal pentatellurides, HfTe 5 and ZrTe 5 , has been measured as a function of temperature and applied magnetic field. At zero magnetic field these materials exhibit a peak in their resistivity ͑at T P) as a function of temperature that corresponds to an, as yet, undetermined phase transition. The application of a transverse magnetic field ͑B Ќ to the current I͒ has a profound effect on the resistive peak in these materials, shifting the peak to slightly higher temperatures and producing a large enhancement of the resistivity at the peak, up to a factor of 3 in ZrTe 5 (T P ϭ145 K͒ and 10 in HfTe 5 (T P ϭ80 K͒. Larger magnetoresistance is observed at even lower temperatures, TϽ20 K. ͓S0163-1829͑99͒06035-X͔